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JATINDER KUMAR
Beginner

Voice Best practice - Quality of service help

friends i have spend my last couple of weeks studying this .. completed a CBT also on QoS but as i am very new need your help in implementing this as this is a production setup.

I have a WAN link of 10MB (F0/0) and LAN side i have multiple sub interfaces (F0/1.x) and one of the sub interface connects to this new client who is having a call center with around 80 agents. 

My current main traffic is email systems. Exchange as we are a hosting company. and then now this new call center client.

as of now their calls are going fine with Qos but i know i will have moments from my other clients/ sub-interfaces when i will have the link getting fully used and then it will become an issue to these calls. which connects to SIP trunk in France.

now what i feel i need is .. that i should be able to configure QoS on my router to give best priority to my voice traffic. and i strongly believe i dont want to do it as per destination but as per nBAR or protocol identification. or may be priority with a fixed bandwidth of 2Mb to this client. I am not sure what will be my steps and how can i achieve this. I have done the theory part but for config can you guys please help me with your experiences.

thanks a LOT. Router wise do i need a special router, currently i have 1841 and CPU load is 30% but i have the option to change the router if i have valid reasons.

14 REPLIES 14
Tagir Temirgaliyev
Frequent Contributor

they installed call center and nobody calculated bandwidth needed? where is it?

according to http://www.cisco.com/c/en/us/support/docs/voice/voice-quality/7934-bwidth-consume.html

for g711 codec 88kbps. 80 agents and can be for example 50 in queue so totally can be 130 calls. so 130*90=11,7 mb

only for call center you need more than you have

hi tagir... codec used is 729

current max users are around 50 so eventually it goes to 8Kbps * 50 = 400Kb

i hope above is simple and correct and i have check with my utilization commands and it doesnt go beyond it.

can you help me now with my initial requirement.

I think before configuring QOS you need to understand what  bandwidth you need to allocate. according to link I provided  729 uses 32 kbps. and 50 agents without queue? so 1,5 mb. are you shure in call center no queue?  

regarding your question about QOS. because we are talking about INCOMING traffic so QOS configuration must be applaied on PE router (Provider Edge)

ok.. true most of the calls are incoming. and for 32Kbps i am OK with that. where i need help is .. if i am having other traffic also going on ... can you help me guiding the way on prioritizing the traffic which matches voice/ rtp

as i dont want that my other client eats all my bandwidth with data traffic and my calls gets affected.

secondly i have the access to edge router. i believe with this you means the router on which ISP providing me the link. ISP wire comes on this router where i have public IPs configured.

on a separate note.. there is a group which makes outgoing calls also.

any help plz.

i have this config from old provider ... can you please explain if i put this will this help

class-map match-any VoIP
 match  dscp ef
 match ip rtp 4659 4659
!
!
policy-map 600k-LLQ
 class VoIP
  priority 900
 class class-default
  fair-queue
  random-detect

I am not able to understand what priority command is doing in this.

Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

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Posting

I am not able to understand what priority command is doing in this.

CBWFQ supports a "special" queue, that has absolute priority over all other queues. This queue is called the low latency queue (LLQ) and is invoked by the priority command.  (NB: you can have multiple LLQ classes, but there's still only one LLQ.)

LLQ enables an implicit policer (per LLQ class) based on the priority command's bandwidth settings.

On many platforms, LLQ only is active when there's CBWFQ queuing.

When active, the implicit LLQ class policer will drop over rate traffic.

LLQ is often used for VoIP bearer traffic.

PS:

I would recommend not using RED with FQ.

wow this made me more confused... friend i am very new to this and i need help for setting up QoS for my voice traffic and i saw this config on the router so i thought asking you guys.

Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

Liability Disclaimer

In no event shall Author be liable for any damages wha2tsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

Ok, in general, for VoIP, you want to prioritize VoIP bearer packets so they are not dropped nor delayed.  You also want to insure VoIP signally packets are not dropped, and not excessively delayed.

How that's accomplished depends on the platform and the circuits you're working with.  For example, in your example of FQ in class-default, on Cisco ISRs, how FQ works differs between IOS pre-HQF vs. post-HQF.  Or, for example, if your 10 Mbps "WAN" is physically running at 100 Mbps, you need to shape for available bandwidth.

There's other considerations too, such as for g729 traffic, you need available bandwidth you can burst into because g729 is VBR (variable bit rate).  (For g729, I would suggest available bandwidth be 2 to 3 times the average g729 used bandwidth.)

Can you help me with this simple thing that if I want my voice traffic should get priority and a certain amount of bandwidth how do I give this 

plz 

Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

Liability Disclaimer

In no event shall Author be liable for any damages wha2tsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

You start by telling us the platform(s) and the IOS(s) used.  You also start by describing the topology.  The you also tell us about the traffic's attribute.  Then you also tell us what you're trying to accomplish.

all is explained in my first post. I am not sure why we are making it so complex. I asked something which is simple i believe sir and i need help on config. but i dont think its that complex. Anyways .. i think i should do my own research

ok

sh runn

sh int  ---- when most intensiv  traffic. interface to provider

sh policy-map